This invention relates generally to fluid powered hammers, and in particular to fluid powered hammers having an impact ram driven by a piston rod of a fluid operated motor for driving piles, breaking rock and pavement, and fill compaction, and similar high-impact related applications.
In typical fluid powered hammers of the aforesaid type, the impact ram is arranged to move generally vertically, such as on a plurality of guide bars, and a hydraulic or pneumatic cylinder has a piston that is connected directly to the impact ram for raising the ram and then driving it downwardly with considerable force to provide an impact force on the object, such as a pile that is being driven into the ground.
To effectuate its intended purpose, the impact ram must have a high level of kinetic energy when it strikes the pile or other object, and, as a result, the impact force transmitted from the piston rod to the impact ram must be a least partially dissipated to avoid damage to the equipment.
In known fluid operated hammers of this type, some form of resilient connection between the piston rod and the impact ram is provided to dissipate the kinetic energy of the piston rod at the point of impact, and such resilient connections take a variety of forms, but in each case the connection is a mechanical connection. For example, in some fluid operated hammers, the piston rod is attached directly to the impact ram using a flange that is sandwiched between a plurality of stacked Belleville washers or similar elastomeric washers in an assembly that is held together by a mechanical connection consisting of a plate held in place by a plurality of bolts.
Another well known arrangement for driving the impact ram consist of a pair of lift cylinders having piston rods disposed externally of the impact ram and mechanically connected to the sides of the impact ram using lift brackets, and a connecting bolt assembly having some form of resilient members to partially dissipate the impact forces transmitted to the impact ram.
While such mechanical connections of this type do act to dissipate some of the severe shock loads that are transmitted between the piston rod and the impact ram by virtue of the Belleville washers or similar elastomeric members, the bolts forming the mechanical connection between the piston rod and impact ram bear the brunt of the severe shock waves created when the impact ram strikes a pile or the like, and, as a consequence, these mechanical connections become loosened or defective in a relative short period of time because of the constant pounding action of the impact ram and the strain waves created by the impact forces generated by the impact ram, and because of the violent accelerations and decelerations of the impact ram in normal usage. Therefore, these mechanical connections must be repaired or replaced on a regular basis, which increases the expense of operating the fluid operated hammer, and the equipment is out of service while it is subject to such maintenance.
In accordance with the present invention, a fluid operated hammer of the aforesaid type is provided which eliminates the mechanical connection between the impact ram and the driving piston rod and the drawbacks associated therewith as described above.